Certain categories of tires are manufactured utilizing a steel cord body ply in which steel cords are embedded into a ply extending from tire bead to bead. In the manufacture of such tires, an initially flat steel cord body ply and other tire components are applied to a building drum at a band diameter to form a green tire. The green tire is subsequently diametrically expanded into a toroidal shape at a toroidal diameter prior to final curing and processing. In the process of changing the carcass from flat to toroidal shape, the cord spacing and cord ends per inch (epi) of wire cords changes. Should ply wire spacing anomalies occur, structural defects in the finished tire can result. Structural defects may be identified at final inspection of the finished tire, requiring the tire to be scrapped, resulting in costly waste. Structural defects in a tire that are not detected at a final inspection may cause tire failure later when the tire is put into use. For example, ply wire anomalies may result in sidewall bulge during the useful life of the tire if the spacing between ply wires is not carefully controlled during carcass expansion. In addition to ply wire spacing anomalies, the integrity and tightness of ply splice regions in the carcass and upstream component preparation of ply splices must be carefully maintained. Compromise of the splice regions as the tire carcass is converted from flat to toroidal shape should be avoided to eliminate structural defects in the finished tire. It is, therefore, important that the integrity of splice regions be maintained during toroidal expansion.
Thus, there is a need for a sensor system that can ascertain the disposition and condition of ply wires in a tire. Evaluating ply wire parameters preferably will occur relatively early in the tire manufacturing process so as to avoid scrapping the finished tire. Evaluating ply wire parameters, however, cannot be accurately conducted when the tire is in a pre-toroidal configuration because subsequent diametric expansion of the tire carcass may alter the condition and disposition of the ply wires and the integrity of splices within the tire carcass.
Commercial systems are available to scan blocks of ply wire as produced from steel cord calenders, or from specialized steel ply making systems. These commercial systems scan steel cords in the flat, unstretched, high epi condition. However, when tires are diametrically expanded on a building drum, typically on the order of 150% to 190% of flat build diameter, the epi count goes down and tire anomalies may appear. Since available systems function in a pre-expansion environment, they are ill suited to detect ply wire anomalies in a post-expansion tire carcass condition. Therefore, such commercially available systems represent a less than adequate solution to the needs of the industry.
A continuing need, accordingly, remains for a sensor assembly that can evaluate ply wire parameters such as ply wire count, and determine if wires are missing or spaced improperly in a post-expansion tire carcass stage. Such apparatus should be capable of functionally checking the integrity and tightness of ply splice regions and upstream component preparation ply splices and determining whether the rubber coat gauge on the steel ply wires is within tolerance limits.